Mechanical factors such as vascular destruction may play a role in some cases, with vigorous peristalsis or increased intraluminal pressure causing shunting of blood into the sub-mucosal arteriovenous system.

The lesions may also resultfrom progressive dilation of normal vascular structures secondary to vascular degenerative changes present in the elderly.

Most angiodysplasias are mucosal and submucosal lesions that are not always grossly visible.

A helpful way to identify the vascular abnormality in resection specimens is to inject an India ink–radiopaque dye combination into the specimen and then to radiograph the specimen and then section it.

Angiodysplasia consists of abnormal numbers of dilated, distorted arteries and veins lined by endothelium and rarely by a small amount of smooth muscle between the pre-existing ectatic arteries, veins, venules, and capillaries.

The earliest abnormality consists ofdilated submucosal veins, which may be present in the absence of mucosal disease.

As the disease progresses, the mucosal abnormalities become more pronounced with increased numbers of dilated and deformed mucosal and submucosal vessels, eventually leading to distortion of the mucosal architecture and erosions.

The vascular channels may be separated from the gastric lumen by a single layer of endothelial cells.

The walls of the vessels in the submucosa appear irregularly thickened.

The presence of distorted and dysplastic vessels distinguishes this lesion from a hemangioma or telangiectasia.